Browsing by Author "Hadjadj, A."

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    Hydrodynamic instabilities in swirling flow under axial magnetic field
    (ELSEVIER, 2021) Laouari, A.; Mahfoud, B.; Bessaïh, R.; Hadjadj, A.
    The present paper investigates numerically the hydrodynamic instabilities occurring in a cylindrical container filled with a conducting viscous fluid and submitted to an axial magnetic field. The axisymmetric swirling flow produced by rotation of the bottom disk, in which a vortex breakdown bubble occurred on the axis of symmetry. This flow structure represents one of the most important instabilities. The governing Navier–Stokes and potential equations are solved by using the finite-volume method. For both steady-state and oscillatory regimes, various combinations of the top, bottom, and side walls conductivity are considered. The effects of the magnetic field and wall electrical conductivities on the position of vortex breakdown and his disappearance is developed. The results obtained showed that the vortex breakdown is suppressed beyond the magnitude of the magnetic field exceeds a critical value. The stability diagram (Ha–Re) corresponding to the vortex breakdown disappearance for electrically conducting and insulating walls is obtained.
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    Study of Ostwald-de Waele fluid flow in an elliptical annulus using the slot model and the CFD approach
    (Taylor & Francis, 2020) Ferroudji, Hicham; Hadjadj, A.; Rahman, M.A.; Hassan, I.; Maheshwari, P.; Odan, M.A.
    Among consequences that can be induced by a non-uniform distribution of the stress and other causes during the drilling process is the elliptical shape of the well and consideration of this effect would improve the accuracy of the drilling fluid hydrodynamics prediction. In the present work, the elliptical shape of the annular space is simplified to apply the slot model taking into account the rotation of the inner cylinder. Moreover, the Slot model results are compared with the experimental data, as well as, with the CFD outcomes where a reasonable concordance is observed, especially for low ratios of the major and minor semi-axis. Also, the CFD results are validated with the experimental data from the flow loop setup. We concluded that the increase of the major and minor semi-axis ratio of the elliptical annulus results in a linear increase of the Ostwald-de Waele frictional pressure loss in the laminar regime for all considered rotation speeds of the inner cylinder. In addition, the increase of the eccentricity from 0 to 0.75 has a positive effect where the frictional pressure loss is decreased by almost 28% for all rotation speeds for the elliptical annulus ((Formula presented.))